1. Field of the Invention
This invention relates to a method to sterilize articles such as medical instruments having long narrow lumens, and more particularly to a method for enhancing the effectiveness of the sterilization of the interior of the lumen.
2. Description of the Related Art
The need to sterilize articles such as medical instruments is well known. There are many methods of sterilization, including heat and chemical methods. Heat sterilization is normally done with steam. The heat or the moisture from the steam treatment damages many medical devices. As a result, chemical sterilization is commonly used.
Chemical sterilization uses a sterilizing fluid such as hydrogen peroxide, ethylene oxide, chlorine dioxide, formaldehyde, or peracetic acid. Although chemical sterilization is normally highly effective, chemical sterilization is less effective with medical devices containing long, narrow lumens, because it is difficult for the sterilizing agent to completely penetrate these long, narrow tubes. In order to enhance the penetration of the sterilizing agent though the entire length of the tube, several methods and several forms of apparatus have been developed to enhance the penetration of the sterilizing agent through long, narrow lumens.
For example, U.S. Pat. Nos. 4,410,492 and 4,337,223 describe an apparatus and a method for sterilizing lumens in which the lumen is placed in a socket connected to a circulating pump. The pump circulates the sterilizing gas through the lumen. Although the method is effective in sterilizing the lumen, the commercial apparatus uses ethylene oxide as a sterilant, and sterilization requires times of about 2-3 hours. Ethylene oxide is toxic. Additional aeration time is needed to remove the residual.
An apparatus and a method for delivering sterilizing agent directly into long, narrow lumens is described in U.S. Pat. Nos. 4,943,414, 5,580,530 and 5,733,503. The lumen is inserted into an adaptor connected to a small vessel containing hydrogen. peroxide. The adaptor and the vessel which contains the hydrogen peroxide are called the booster. The lumen, vessel, and adaptor are placed into a sterilization chamber. When the sterilization chamber is evacuated, the hydrogen peroxide vaporizes and passes through the lumen, providing the necessary hydrogen peroxide to the interior of the lumen. Although effective, the method has some disadvantages. First, in some forms of the apparatus, the booster must be xe2x80x9cactivatedxe2x80x9d manually by piercing a septum to make the hydrogen peroxide liquid accessible. Second, the booster is used only once before it is discarded. Third, the product has a limited shelf life. The storage and shipping conditions may affect the shelf life of the product.
There is a need for a method of sterilizing lumens which does not require the use of a booster with limited shelf life. Further, there is a need for a method which utilizes an apparatus which is reusable, to reduce costs.
One aspect of the invention involves a method for enhancing the sterilization of a lumen, where the lumen encloses an internal volume. The method includes attaching a dry booster to an end of the lumen, where the internal volume of the dry booster is at least 2 times the internal volume of said lumen and where the dry booster does not contain liquid. The method also includes placing the lumen and the dry booster in a chamber, introducing germicide into the chamber, and creating a higher pressure outside the dry booster than inside the dry booster. The method also includes flowing germicide from the chamber into the dry booster through the lumen, and sterilizing the lumen.
Advantageously, the dry booster includes an adaptor. Preferably, the dry booster includes a vessel. In some embodiments, the dry booster includes a flow restrictor. Advantageously, the dry booster includes a check valve. In an embodiment, the lumen is a plastic lumen. In another embodiment, the lumen is a metal lumen. Advantageously, the volume of the dry booster is at least 3 times the volume of the metal lumen.
The method may also include reducing the pressure in the chamber, evacuating the dry booster. Preferably, the pressure in the chamber is reduced below the vapor pressure of the germicide. Advantageously, the method also includes venting the chamber. Preferably, the method also includes generating a plasma in the chamber. In an embodiment, at least one step is repeated. Preferably, the germicide is a liquid, vapor, or gas. Advantageously, the germicide is hydrogen peroxide, ethylene oxide, peracetic acid, chlorine dioxide, or formaldehyde.
Another aspect of the invention involves a system for sterilizing a lumen, where the system includes a vacuum chamber, a pump to evacuate the chamber, a dry booster, where the dry booster is attachable to and detachable from the lumen, and where the internal volume of the dry booster is at least 2 times the volume of said lumen; and a source of germicide.
Preferably, the dry booster includes an adaptor. Advantageously, the dry booster includes a vessel. In an embodiment, the booster includes a flow restrictor. In another embodiment, the dry booster comprises a check valve.